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Why are there two current ratings for power inductors?
Aug 31, 2018


Why are there two current ratings for power inductors?


In a DC-DC converter, the inductor is the core component next to the IC. Higher conversion efficiencies can be achieved by choosing the right inductor. Therefore, the main parameters of the inductor corresponding to the inductor are selected: inductance value, rated current, size, etc., and these parameters also include the concept specific to the inductor. For example, there are two kinds of rated currents for power inductors. What is the difference between them?




To understand the difference between them, you first need to understand the reasons for the two current ratings. The rated current of the power inductor has two determination methods: "rated current based on self-temperature rise" and "rated current based on change rate of inductance value", which are of great significance. "Rated current based on self-temperature rise" is the rated current specification based on the calorific value of the component. When it is used outside the range, it may cause component damage and component failure.




At the same time, the "rated current based on the rate of change of the inductance value" is defined as the rated current of the degree of decrease in the inductance value. When the range is exceeded, the IC control may be unstable due to an increase in ripple current. Further, depending on the magnetic circuit configuration of the inductor, the tendency of magnetic saturation (i.e., the tendency of the inductance value to decrease) is different. The figure below is a schematic diagram showing changes in inductance values caused by different magnetic circuit configurations. With regard to the open circuit type, as the DC current increases, a relatively flat inductance value appears until the predetermined current value, but the value of the boundary current decreases sharply with the predetermined current value. On the contrary, as the DC current type increases, the value of the permeability decreases gradually, so the inductance value slowly decreases.


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